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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 36 |
| 3 | 126 |
| 4 | 756 |
| 5 | 2016 |
| 6 | 23976 |
| 7 | 46956 |
| 8 | 435456 |
| 9 | 1683576 |
| 10 | 15128856 |
| 11 | 36284472 |
| 12 | 547204896 |
| 13 | 1088416056 |
| 14 | 13060989936 |
| 15 | 58782164616 |
| 16 | 352913845536 |
| 17 | 1057916846196 |
| 18 | 16926689693376 |
| 19 | 33853322280036 |
| 20 | 457078896068256 |
| 21 | 1828085963706576 |
[6,36,126,756,2016,23976,46956,435456,1683576, 15128856,36284472,547204896,1088416056, 13060989936,58782164616,352913845536, 1057916846196,16926689693376,33853322280036, 457078896068256,1828085963706576] |